1. Field of the Invention
The present invention relates to a semiconductor element manufacturing method and to the construction of an element manufactured using the method, and particularly to a deposition method for a thin film used as wiring and a laminated construction for a thin film deposited using this method.
2. Description of the Related Art
In the case of forming an element on a conventional semiconductor substrate, a wiring thin film deposition method as shown in FIGS. 1–3 is carried out. First of all, an insulating film 2 (for example, SiO2 BPSG) is deposited on a semiconductor substrate 1 typically of a material such as silicon, and a barrier layer 3 (for example, Ti, TiN or a laminate of the two) is deposited. Next, an Al film is deposited with the semiconductor substrate heated to 150–400° C., by a sputtering method using an Al—Si—Cu target having Si added to 0.05–1.0% which is at least the solution limit of Al.
Here, Si is added to improve EM (electromigration) resistance. Also, the reason for heating the semiconductor substrate at the time of Al deposition is to increase the size of the Al grains (crystal grain) to increase EM resistance, and to improve step coverage. Next, an antireflection membrane (ARM) 5 that is, for example, Ti, TiN or a laminate of the two, is deposited, preferably by performing a photolithography process. After that, wiring is patterned using a well known photolithography method or etching method.
However, with the Al thin film sputter deposited using an Al—Si—Cu target having Si added to at least the solution limit of Al as described above, there are the following problems. Specifically, at the time of depositing the Al film, deposited Si particles 6 are dissolved in the Al due to the high heating temperature of the deposition, and in a process of cooling the wafer gradually after deposition from the deposition temperature there is a nucleus of remaining Si that could not be dissolved. Recrystallization growth of the temporarily dissolved Si starts, as a result of which an enormous Si deposit 7 is formed (refer to FIG. 4(1)-(3). This Si deposit 7 deposited in the Al film is not removed by etching gas in the Cl2 family that is normally used at the time of etching the Al film in a subsequent step, and as a result remains as an Si residue. As shown in FIG. 5, this Si residue 8 unfortunately acts as a mask at the time of etching the Al underneath the residue. Because of this, pattern defects arise, and if the size of the Si residue becomes larger than an interval between wires in the wiring pattern this will cause shorting between wires.